The invention relates to pneumatic vehicle tires.
A pneumatic vehicle tire of this kind is known from EP 0 822 105 A2. Furthermore, a similar pneumatic vehicle tire is described in U.S. Pat. No. 5,511,599. By means of such tires it is possible, in the event of a tire puncture, to travel larger distances at adequate speed, even with a deflated tire, before repair of the tire or a tire change has to be effected. Such tires accordingly increase the safety in the event of a tire puncture and make it possible to reach the next repair shop without problem, so that undesired and also dangerous tire changing on roads with heavy traffic can be avoided.
The object of the present invention is to design a pneumatic vehicle tire of the initially named kind so that even in the deflated state a long distance can be traveled at an adequately high speed, so that the stiffening rubber plies in the side walls do not disturbingly impair the driving comfort of the tire operated at normal pressure and so that the tire weight remains as low as possible.
This object is satisfied starting from a pneumatic vehicle tire of the kind initially mentioned in that the three rubber reinforcing plies extend, starting from the bead apex region, with mutually displaced ends up to and beneath the edge region of the belt ply; and in that all rubber reinforcing plies and also the bead apex consist of the same rubber mixture whose modulus of elasticity of the rubber reinforcing plies and also of the bead apex is the same as or greater than 9 MPa when measured at 70xc2x0 C. and the tans is the same as or smaller than 0.03, and indeed measured by means of xe2x80x9cEPLEXORxe2x80x9d: 10 Hz, 10% prestress and 1% DSA (double strain amplitude).
As a result of the choice of the rubber mixture, of the thickness profile of the rubber reinforcing plies and of the differing hardening times of these rubber reinforcing plies in dependence on the position of the rubber reinforcing plies in the tire, ideal values are obtained with respect to the long running characteristics with the deflated tire. The hardness IRHD of these rubber reinforcing plies and also of the bead apex should be equal to or greater than 80 when measured at room temperature, The measurement of the IRHD (International Rubber Hardness Degree) thereby takes place analogously to the Shore hardness measurement, but with a ball like measuring tip. The measurement or testing thereby takes place in accordance with DIN 53519, with the so-called microhardness being determined, since small samples are measured which are taken from the respective tire.
The rubber reinforcing plies and bead apex are preferably manufactured from a rubber mixture which consists of a polymer mix of NR/IR and BR, with at least 50 parts of NR/IR being contained in this polymer mixture, a carbon black content of 50 to 60 parts, preferably a rapidly sprayable FEF carbon black, as well as 5 to 8 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of aging protecting agent and also one or more parts of vulcanization accelerator and sulfur (preferably 4 to 5 parts) in order to keep the loss characteristics of the mixture low. All parts are parts by weight.
An advantageous embodiment is characterized in that all rubber reinforcing plies taper to a tip at their free ends in cross-section.
In the event that the radially inner end of the outer rubber reinforcing ply is simultaneously formed as a bead apex, provision is made that, when measured in the region of the maximum bead thickness (side wall height W), the thickness of the inner rubber reinforcing ply is approximately 2.5 mm, the thickness of the middle rubber reinforcing ply is approximately 1.9 mm, and the thickness of the outer rubber reinforcing ply amounts to 6.9 mm, with a tolerance of +/xe2x88x920.5 mm applying for all measured values.
Accordingly, in one preferred form there is provided a pneumatic vehicle tire comprising a multi-ply carcass, which extends between two bead cores having associated bead apexes, a belt arrangement provided between the carcass plies and a tread strip and also rubber reinforcing plies arranged in the side wall regions, which take on a supporting function with a deflated tire, wherein a first rubber reinforcing ply is arranged radially inside a first carcass ply, a second rubber reinforcing ply is arranged between the first carcass ply and a second carcass ply, a third rubber reinforcing ply is arranged between the second carcass ply and a third carcass ply, and the three rubber plies have a different height in the radial direction and different thicknesses over the height of the side wall; and wherein the radially inner end regions of all three rubber plies are disposed on the axially inner side of the bead apex, and the ends of the radially innermost, first, carcass ply are led around the respective bead core and are overlappingly connected to the respective end of the outer, third, carcass ply, and the middle carcass ply terminates axially inside the bead apex adjacent to the respective bead core, the tire characterized in that the three rubber reinforcing plies extend, starting from the bead apex region with mutually displaced ends up to and beneath the edge region of the belt arrangement; and the tire further characterized in that all rubber reinforcing plies and also the bead apex consist of the same rubber mixture whose complex modulus of elasticity (E*) of the rubber reinforcing plies and also of the bead apex is the same as or greater than 9 MPa and the tan xcex4 is the same as or smaller than 0.03, measured at 70xc2x0 C., 10 Hz, 10% prestress and 1% double strain amplitude (DSA).
In one form, all three rubber reinforcing plies have a different thickness over their height and the middle rubber reinforcing ply has a lesser thickness over an at least predominate part of the side wall height in comparison to the inner and outer rubber reinforcing plies.
In another form, the tread side ends of the rubber reinforcing plies terminate with an increasing distance from the central plane of the tire, starting from the radially innermost ply.
In another form, the radially inner end of the radially outer rubber reinforcing ply contacts the inner side of the bead apex.
In another form, the middle carcass ply is connected in a region lying above the bead core to the radially inner carcass ply.
In another form, the carcass plies consist of rayon.
In another form, the belt plies consist of Kevlar (aromatic polyamide) or steel and the belt is optionally stiffened by additional rubber between the belt plies.
Further advantageous embodiments of the invention are set forth in the subordinate claims and will also be explained in the description of the embodiments.